In the last several years there has been an explosion of information regarding the nature of peptide antigens expressed on human tumors together with class I molecules encoded in the Major Histocompatibility Complex (MHC) and recognized by cytotoxic T lymphocytes (CTL). One very successful approach aimed at the identification of these antigens, termed Direct Identification of Relevant Epitopes for Cancer Therapeutics or DIRECT TM, was developed by Argonex consultants. This technology involves the extraction and separation of class I MHC associated peptides, analysis for recognition of peptide-containing fractions using CTL from patients, and identification of the antigenic peptides by tandem mass spectrometry. In this Phase I application, we propose to employ DIRECT to isolate and identify one or more peptide antigens that are expressed on a human squamous cell cancer of the lung (SCCL) in the context of the human class I MHC molecule HLA-A68 and recognized by patient CTL. This research will lead to a more comprehensive analysis, using DIRECT, of antigens on SCCL recognized by CTL, including identification of the source proteins and an assessment of whether these or other peptides derived from the same proteins are recognized by CTL from other SCCL patients. PROPOSED COMMERCIAL APPLICATION: Non-small cell Lung cancer is the most common malignancy m the U.S. for both men and women, and roughly half of these cases will be squamous cell tumors. More than half of the patients diagnosed with the disease have metastases at initial diagnosis and, therefore, are not curable by surgery or chemotherapy. The development of immunotherapeutic approaches based on antigens recognized by tumor specific CTL offers a significant commercial opportunity.